Abstract
The influence of acid solutions was investigated on the mechanical properties of mudstone. Uniaxial compression tests on mudstone samples were conducted to determine the variations of relative mass, porosity, deformation, and strength characteristics of mudstone subjected to acidic solutions with different pH values. The change of pH, relative mass, and porosity of mudstone in the process of acid solution immersion was monitored during soaking. The mechanism of hydrochemical corrosion of mudstone samples was preliminarily discussed. The damage parameter was introduced based on the porosity rate. The results show that with increased solution acidity, the peak stress and elastic modulus decreased to different levels, while the peak strain increases in the rock samples. The increased chemical damage parameters reduce the mechanical parameters and increased the deformation parameters. On the basis of the mechanical test, considering the stress-strain relationship of rock in the compaction stage, a segmented damage constitutive model of rock based on chemical damage parameters is established, and the test results are verified. The results show that the correlation coefficient between the theoretical curve and the experimental data is as high as 0.98, and the model is suitable for the analysis of chemically corroded rock under the uniaxial compression test. The results provide a reference for the analysis and design of coal-bed methane wells where the rocks frequently become acidic during the production of methane.
Highlights
Coal-bed methane (CBM) is a clean and efficient energy source associated with coal seams [1,2,3]
In this paper, the uniaxial compressive stress-strain curve of rock soaked in acid water is divided into the compaction stage and subsequent damage expansion stage, and a separate damage constitutive model is established
The following are the conclusions of the research: (1) The peak stress and elastic modulus of rock samples decrease to different degrees with the increases of solution acidity, but the peak strain increases with the increase of solution acidity, and the proportion of compaction stage increases with the increase of acidity
Summary
Coal-bed methane (CBM) is a clean and efficient energy source associated with coal seams [1,2,3]. A hydrochemical solution has certain adverse chemical effects on the mineral composition of the rock and the cementing properties between the mineral particles. This chemical effect plays a significant role in changing the original structure of the rock and can even produce new minerals [8,9,10,11]. This in turn affects the process of desorption, diffusion, and seepage interaction of coal-bed methane in the reservoir. It is of great significance to study the physical and mechanical properties of the rock corroded by chemical water in order to ensure the efficient exploitation of coal-bed methane
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